The applications of these systems entail the transmission of high-speed data between two mobile devices (two portable telephones, for example) or a mobile device and a fixed device (a portable telephone and a computer, for example), contactless transmission between two electronic chips or two chip cards, transmission of a video stream between an Internet network connection box (set top box) and a television receiver, etc.
The millimeter band considered in this invention is a frequency band generally referred to as the 60 GHz band, i.e. radio carrier frequencies between 57 and 66 GHz, but the invention would also be applicable to other frequency bands, both below 57 GHz and above 66 GHz, for example from 10 to 100 GHz.
The term 60 GHz signal will be used below for simplicity to qualify the radio frequency signal transmitted or received by radio link.
In the prior art, implementations have been proposed which differ from one another according to the desired transmission range.
When the range is very short, in the region of a few millimeters, each card has a transmitting/receiving integrated circuit connected to a respective antenna. This is the case, for example, when a communication is to be established between two chip cards: they are brought quite close to one another and their antennas are located a few millimeters at most from one another. The transmitting/receiving circuits and the antennas to some extent replace an electrical connection by direct contact. The patent publication US2010159829 and the U.S. Pat. No. 7,808,798 describe transmitting/receiving circuits in this context.
When the range is longer (several tens of centimeters to several meters), it has already been proposed to transmit or receive the radio frequency signal in parallel on N channels connected respectively to N antennas; a directional beam-formation effect is produced by a control of the phase shifts of the carrier frequency in each of the channels.
For transmission, a processor produces a baseband modulation signal, which is then frequency-transposed by a 60 GHz radio frequency transmitter. The signal is then divided among N channels by power dividers, and is then selectively phase-shifted on each channel and amplified to be fed to a respective antenna.
Similarly, on reception, a network of N antennas (which may be the same as the transmit antennas) receives the signal and feeds it to a series of N amplifiers and phase shifters; the phase shifters serve to compensate individually the phase differences of the signals received by the different antennas in one spatial direction; the phase-shifted signals are recombined by a combiner (similar to the power divider which is used for transmission, but operating in the opposite direction), before entering a radio frequency receiver which carries out the frequency transposition to the baseband, and then entering the signal processing processor.
In this architecture, the signal processor which generates the radio frequency signal or which receives the recombined signal, the power splitter, the combiner, and each of the transmitting/receiving circuits which selectively phase-shift and amplify the signal transmitted or received by a respective antenna are assembled on the same integrated circuit chip. The antennas are preferably implemented outside the integrated circuit due to the fact that the silicon substrate of the integrated circuit does not lend itself well to an antenna usage (it is generally too conductive). The antennas may be formed on a standard plastic or ceramic printed circuit board, on which the integrated circuit is disposed.
This beam-forming architecture for a long-range communication results in a large-surface and therefore costly integrated circuit chip, which may be acceptable for a long-range communication but is unacceptable for a short or medium-range communication, since the latter can be implemented with a much cheaper integrated circuit chip. Moreover, this architecture is not versatile, since a costly development must be repeated for each new application. Patent publication US20090061795 describes an example of an architecture of this type.